The disclosure relates to methods of making bisphenol employing an acidic ion exchange resin. In particular, the disclosure relates to methods of making bisphenol employing an acidic ion exchange resin and a promoter.
Typical bisphenols, such as 4,4′-isopropylidenediphenol, e.g., bisphenol-A (BPA), are widely employed as monomers in the manufacture of polymeric materials, such as engineering thermoplastics. For example, BPA is a principal monomer used in the manufacture of polycarbonate. Bisphenols are generally prepared by the electrophilic addition of aldehydes or ketones such as acetone to aromatic hydroxy compounds such as phenol, in the presence of an acidic catalyst composition. These types of reactions are also referred to as acid catalyzed condensation reactions. Commercially sulfonated polystyrene resin cross-linked with divinylbenzene, (PS-DVB) is typically used as the solid acid component of the catalyst composition. Reaction promoters can also be employed as part of the catalyst composition to improve the reaction rate, and selectivity, of the desired condensation reaction; in the case of BPA, the desired selectivity is for the para-para isomer. Promoters can be present as unattached molecules in the bulk reaction matrix, e.g., “bulk-promoters”, or can be attached to the resin through ionic or covalent linkages, e.g., “attached-promoters”. A useful class of promoter is the mercaptans, specifically thiols, e.g., organosulfur compounds which are derivatives of hydrogen sulfide.
There has been much published with regard to the use of bulk and attached promoters but much of the previous work has been related to small scale reactions that are typically performed in a batchwise fashion. There can be significant technical difficulty in applying attached promoters to large, commercial scale reactions, especially large scale reactions run in a continuous fashion.